The present invention relates generally to a system and method for identifying wear of a welding-type consumable and, more particularly, to a system and method for indirectly determining consumable wear by identifying symptoms of wear conditions, such as micro-arcing.
Welding is a common process that often employs a consumable electrode in the form a welding wire that is fed to a weld point through a welding gun. The welding gun, among other components, may include a nozzle surrounding a tip or contact tip. The contact tip forms an axial bore through which the wire is fed to exit the welding gun. In this regard, the contact tip forms a sliding electrical contact through which power delivered from a welding power source is transferred to the wire.
By energizing the wire, the wire acts as an electrode that extends from the welding gun. When positioned near a grounded workpiece, an electrical current passes through the welding wire to the workpiece and causes the welding wire and workpiece to be heated and melt. The melted welding wire is propelled toward the workpiece where it fuses with the workpiece to effectuate the weld.
Over time, the tip and even the surrounding nozzle can begin to wear. These worn areas can cause the high currents used to perform the welding process to be localized around small areas that induce the welding wire to stick or adhere to the tip. These inconsistencies in wire feeding can result in poor welds. Accordingly, it is desirable to identify this phenomenon, typically referred to as micro-arcing or dingus, and replace the tip before an inconsistent weld or weld of poor quality is created.
In manually controlled welding systems, skilled operators are trained to identify the intermittent vibrations that are caused when the wire sticks to the contact tip as an indicator that the contact tip should be cleaned or replaced. The tip may also display movement of the contact area and varying impedance levels as the contact tip starts to degrade. Operators may also see arc instability or an erratic arc during and or prior to intermittent vibration due to contact tip degradation. However, in automated welding systems or in manual welding systems directed by an operator who has not been trained to identify these intermittent vibrations, the micro arcing may be permitted to continue until the wire eventually welds to the contact tip of the welding gun. In this case, the welding process is forced to cease due to this impediment to proper wire feeding. Beyond the fact that these intermittent feeding and instability issues occur and potentially create poor welds and interfere with efficient welding processes, they can yield excessive waste and repair time that otherwise could have been avoided if the contact tip was replaced earlier.
Accordingly, some systems have been developed that attempt to directly monitor the contact tip to identify wear conditions. For example, some systems include a sensor that monitors the resistance between the contact tip and electrode to identify changes in the resistance indicative of tip wear. However, such systems require multiple sensors arranged throughout the welding system, which requires that the primary hardware components of the welding system are specifically designed to perform such monitoring. In particular, the resistance is typically determined by calculating the ratio of the instantaneous voltage drop at the contact interface to the instantaneous welding current. In this case, a voltage sensor system must be included that is designed to measure the voltage between the electrode and the power supply. Hence, both the power supply and the welding gun must be specifically designed to calculate this voltage. In addition, the welding current is typically measured by a current sensor associated with the welding gun. Accordingly, though such wear detection systems have been developed, they are relatively complex and can be difficult to integrate with traditional welding systems that do not include the requisite sensor systems. Furthermore, these systems can be susceptible to “false positives” caused by variations in the welding power that are not attributable to contact tip wear.
Therefore, it would be desirable to have a system and method to identify worn consumables, including contact tips and welding wire, that does not require complex distributed sensor systems to directly monitor the contact tip. Furthermore, it would be desirable to have a system and method for indicating and/or automatically correcting a worn consumable.